It is well known that application of chemical sprays to many agricultural and horticultural crops results in a serious loss of expensive chemicals, and this in turn results in a chemical contamination of the environment which is sometimes regarded as a major problem.
With spray patterns which have been developed for the spraying of vineyards, orchards, and other crops such as lettuces, there has quite often been a loss of between 60% and 80% of the applied spray volume which fails to adhere to the foliage. This is particularly true of air-mist sprayers where a high velocity is used to promote spreading of the spray throughout the foliage. Overspray often results in large clouds of spray mist being released into the atmosphere and being able to drift onto open ground, into houses and in other ways cause chemical contamination.
However in order to create adequate foliage cover, a considerable velocity is applied to the droplets of spray, and this renders difficult the containing of any spray. This is true both for air-mist or direct spray mist jets, and also to electrostatic spraying although the latter is obviously more efficient.
This invention relates to improvements in spraying of crops in general, and is particularly useful in the spraying of grape vines, pome and citrus trees. Grape vines require repeated spray applications once the shoots are approximately 10 cm long. A trellised vine at that stage comprises foliage along the lateral canes, with the greater amount near the trunk area. The height of the trellis above the ground is usually constant, but the ground often undulates due to contoured vineyards. It is therefore quite difficult to achieve a spray pattern which is adequate for the canes and which will also cover the trunk area, and be able to accommodate varying heights. It is in such circumstances that one can expect as much as 80% loss.
When pome or citrus trees are subjected to pressure spray only, the leaves usually close against one another, and inhibit penetration of spray into the tree. Applying a suction on the lee side of the tree causes leaf flutter in a manner which greatly improves spray coverage.